(i) Technical Field
The present invention relates to aperture devices and optical instruments.
(ii) Related Art
Japanese Unexamined Patent Application Publication No. 2009-31663 discloses an aperture device in which a diameter of an opening formed in a board is adjusted by blades.
For example, when the blades stop in respective desired positions, the impact is applied to the aperture device, so the blades might be positionally displaced from the respective desired positions. In particular, when the blades stop in a non-energized state of a motor serving as a drive source for the blades, the above situation might occur. Further, in a case of using a stepping motor as the drive source, a rotor might stop in an unstable position because of the property of this motor. In such a case, the impact is applied to the aperture device, so the blade might be positionally displaced.